While giving any presentation or while speaking to an audience, not just our words but also our body language ascertains our confidence and authority in front of them. Which is why, it becomes necessary to make sure that what we speak verbally as well as through our body compliments each other.
Making eye contact with the audience ensures that they would be paying attention to whatever you have to say and the use of small, stiff gestures guarantees that you exude the right amount of authority on your audience.
Using positive gestures, engaging with your hands and smiling often makes sure that when you want to convince them of your point, they are actually thinking on the lines of your speech. See the Infographic for wonderful tips that will make you a powerful speaker.